IMC · 2021 International Mechanical Code
§403.3.1 · Exhaust rate table (Table 403.3.1.1)
Effective in IMC 2021 · IMC 2024 SE Wisconsin · IMC 2024 NW Indiana.
Plain-English explainer
403.3.1 (Table 403.3.1.1) sets the local-exhaust rate for kitchens, baths, and similar rooms — commercial kitchens need ≥100 cfm intermittent or 25 cfh per ft² for the duty. The drafter cites this when a commercial permit mentions a Type I or Type II hood.
Why inspectors flag this
A commercial kitchen with a 100-cfm exhaust where the hood is rated for 400 is the canonical 403.3.1 failure; the drafter lifts the rule so the rough-in matches the design before the inspector walks the site.
As quoted in the code: Kitchens, baths, and similar rooms need a local exhaust sized by the table — for example, commercial kitchens take at least one hundred cfm intermittent, or twenty-five cfh per square foot for the duty.
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